Suspensions for suspending sliders in hard disk drives are well known in the art. Referring to FIG. 1, in a typical hard disk drive, the drive's read-write transducer 10 is included in, or mounted to, a slider 12, which has an aerodynamic design and is supported by a suspension 14. The slider's aerodynamic design allows for airflow between the slider and the disk drive's spinning disk 16. This airflow generates lift, which allows the read-write transducer to fly above the spinning disk's surface 18 at an optimal distance for reading data from, or writing data to, the disk. Referring additionally to FIG. 2, which is a partial side elevational view of the slider and a distal end 20 of the suspension, a typical suspension includes a gimbal 22 at the suspension's distal end, a load beam 24, and a baseplate 26 at the suspension's proximal end 28. The slider is bonded to the gimbal, which permits the slider to pitch and roll as it tracks fluctuations in the surface of the disk, and the gimbal is bonded to the load beam's distal end using, for example, a welding device, e.g., a spot welding device.
Typically, the load beam 24 is formed from stainless steel (“SST”) foil and includes a spring portion 30 that applies a loading force, also known as a “pre-load” or “gram force,” to the slider 12. The pre-load force counteracts the lift that is generated by the interaction between the slider and the spinning disk 16, and brings the slider into a predetermined close spacing to the disk surface 18 while the disk is spinning. A proximal end 32 of the load beam is coupled to the baseplate 26, which is configured to couple to an actuator arm 34. The actuator arm moves under motor control to precisely position the slider, and thus, the drive's read/write head 10 relative to the disk surface.
As shown in FIG. 2, the gimbal 22 supports the slider 12. In particular, the slider is coupled to a tongue-shaped part 36 of the gimbal. The distal end 38 of the load beam includes a hemispherical projection (also referred to as a dimple) 40 against which the tongue-shaped part of the gimbal rests. The gimbal in combination with the load beam's hemispherical projection allows the slider to pitch and roll in response to irregularities in the disk's surface 18.
Referring additionally to FIGS. 3 and 4, an example gimbal 22 is shown. FIG. 3 is a partial top plan view of the example gimbal, which includes two struts (also known as “outrigger struts”) 42 and 44 that couple the gimbal's tongue-shaped part 36 to the gimbal's proximal end 46, which couples to the distal end 38 of the load beam 24. As shown in the sectional view of FIG. 4, the strut includes the following three layers: a supporting layer 48, a conducting layer 50, and an insulating layer 52, which is coupled between the supporting layer and the conducting layer. The supporting layer is configured to provide mechanical support for the insulating and conducting layers. Typically, the supporting layer is made of a supporting material, e.g., stainless steel (“SST”). The insulating layer (also referred to as a “dielectric layer”) is made of an insulating material, e.g., polyimide. The conducting layer is made of a conducting material, e.g., copper or an alloy thereof, and formed into traces 54 that are configured to be coupled to electrical leads (not shown) that interface with the slider's read-write transducer 10. Overall, the strut, including all three layers, has a height “HS” and a width “WS.”
The size of disk drive sliders 12 has decreased over time. As sliders have become smaller, the requirements for disk drive suspensions 14 have shifted to ever lower pitch and roll stiffness values because a smaller slider will exert a smaller torque on the disk drive suspension. Accordingly, the disk drive suspension's pitch and roll stiffness values must be lower so the slider is still able to maintain its pitch and roll within a specific range while the slider flies above the disk's surface 18 under a variety of conditions, e.g., vibration of the disk drive.
Various schemes have been developed to achieve suspensions 14 having low pitch and roll stiffness values. In one scheme, the height “HS” and the width “WS” of the gimbal's struts 42 and 44 are minimized by making the height and width of the individual layers, i.e., the supporting layer 48, the insulating layer 52, and the conducting layer 50, of each strut as small as possible. However, the dimensions of the layers cannot be reduced below the manufacturing capabilities of the equipment that is used to fabricate the layers. Accordingly, there are inherent limitations in the fabrication process that prevent the reduction of a disk drive suspension's pitch and roll stiffness values beyond a certain value.
In other schemes, the layers 48-52 that make up the gimbal's struts 42 and 44 are separated lateral to one another in an effort to reduce the high values of pitch and roll stiffness that occur when the layers are stacked vertically on top of one another, as shown in FIG. 4. A difficulty that is associated with this approach is that when the layers of the strut are dispersed laterally and are very thin, the layers are subject to vibrations due to impinging airflow from the spinning disk 16.
Another difficulty that is associated with gimbal's struts 42 and 44 having laterally separated layers 48-52 is that it is difficult to include a ground plane in these struts. In the past, due to concerns over the mechanical performance of gimbals 22, ground planes were not used in struts in an effort to keep pitch and roll stiffness values low. As disk drive data rates have increased over time, the inclusion of a ground plane in the gimbal has taken on importance because the ground plane advantageously offers reduce impedance discontinuity at the interface between the suspension 14 and the read-write transducer 10.
It should, therefore, be appreciated that there is a need for a disk drive suspension 14 that includes a gimbal 22 having a low value of pitch and roll stiffness, and that can be manufactured using currently available fabrication techniques without compromising vibrational and electrical performance. The present invention satisfies these needs.